Data transmission method and apparatus

ABSTRACT

Embodiments of this application provide a data transmission method and apparatus. The method includes: receiving data sent by a terminal in an inactive state, where the data includes to-be-sent data sent by the terminal and identification information of the terminal; determining an anchor base station of the terminal based on the identification information; and sending the data to the anchor base station, so that the anchor base station sends the data to a core-network device. The uplink data of the terminal is forwarded to the anchor base station by using a serving base station and through an interaction between the anchor base station and the serving base station that currently provides an air interface resource for the terminal, and is then transmitted to a core network.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/CN2017/112527, filed on Nov. 23, 2017, which claims priority toChinese Patent Application No. 201710008537.6, filed on Jan. 5, 2017.The disclosures of the aforementioned applications are herebyincorporated by reference in their entireties.

TECHNICAL FIELD

Embodiments of this application relate to communications technologies,and in particular, to a data transmission method and apparatus.

BACKGROUND

With development of network technologies and popularization of mobileterminal devices, scenarios in which users send or receive data by usingmobile terminal devices become more common. A device such as a mobilephone remains in a network-connected state even if no data needs to besent or received. To save network resources, a concept of a lightconnected state/an inactive state is proposed. The light connected stateis used in a long term evolution (LTE) network. A state referred to asthe inactive state is introduced in a new (RAT) such as 5G. Behavior inthe state is similar to that in the light connected state in LTE, and ismerely to retain a connection that is between a core-network node and anaccess network and that serves UE.

FIG. 1 is a schematic diagram of a tracking area update of UE data. Asshown in FIG. 1, an interface that is between a CN and a radio accessnetwork (RAN) and that serves a terminal (UE) in “a light connectedstate/an inactive state” is anchored to a RAN node (for example, ananchor base station eNB 1, that is, a base station to which the UE isconnected during movement to transmit data). The UE does not need tonotify the base station when the UE moves within a predefined area(referred to as a notification area in 5G and referred to as a pagingarea in LTE, that is, a tracking area of the eNB 1 in FIG. 1). However,once the UE is out of the area and moves into a tracking area of an eNB3, the UE needs to notify the base station eNB 3 of a location of theUE, that is, perform a tracking area update process. When the UE in the“light connected state/inactive state” moves to another base station andneeds to send data, the UE initiates a connection recovery process to aserving base station, and enters an active state. The serving basestation is a base station to which a cell providing an air interfaceresource for the UE belongs. The serving base station initiates acontext request for the UE to the anchor base station, to migrate acontext of the UE to the serving base station eNB 3 to which the UEbelongs; at the same time, a path switching request is sent to acore-network node, to switch a connection path S1 corresponding to theUE to the serving base station. Only then can data transmission of theUE be implemented.

However, in the foregoing manner, each time a serving base station ofthe UE changes, context migration and switching of a connection betweena core network and a base station need to be performed and an anchorbase station needs to be changed. Change of the anchor base stationresults in a UE key update and context obtaining. This causes relativelyhigh signaling overheads during movement of the UE. When the UE movesbetween two base stations, the context of the UE is frequently migratedbetween the two base stations, and interface overheads between the basestations and the core network and air-interface radio resource control(RRC) signaling overheads are high.

SUMMARY

Embodiments of this application provide a data transmission method andapparatus, so as to resolve the following problem: Relatively highsignaling overheads are caused during movement of a terminal, and whenthe terminal moves between two base stations, a context of the terminalis frequently migrated between the two base stations, and interfaceoverheads between the base stations and a core network and air-interfaceRRC signaling overheads are high.

According to a first aspect of the embodiments of this application, adata transmission method is provided. The method includes receiving, bya serving base station, data sent by a terminal in an inactive state,where the data includes to-be-sent data sent by the terminal andidentification information of the terminal. The method also includesdetermining, by the serving base station, an anchor base station of theterminal based on the identification information. The method alsoincludes sending, by the serving base station, the data to the anchorbase station.

This solution is performed by the serving base station. Uplink data ofthe terminal is forwarded to the anchor base station by using theserving base station and through an interaction between the anchor basestation and the serving base station that currently provides an airinterface resource for the terminal. The anchor base station sends thedata to a core-network device. Neither context migration nor switchingbetween a core network and a base station needs to be performed.Therefore, signaling and interface overheads are reduced, and datatransmission efficiency is improved.

In a specific implementation, the method further includes: receiving alogical channel identifier corresponding to the data sent by theterminal; and sending, to the anchor base station, an IP flow identifierand/or a logical channel identifier and/or a channel type correspondingto the to-be-sent data, where the logical channel identifier is includedin the data or not included in the data.

In a specific implementation, the identification information includes: aunique identifier used to indicate the terminal in an access-networknotification area in which the terminal is located; or a cell radionetwork temporary identifier (C-RNTI); or an identifier allocated by acore-network device.

In the foregoing solution, the identification information may furtherinclude information indicating the anchor base station to which theterminal belongs, that is, the identification information of theterminal may be configured identification information specially used toidentify the anchor base station of the terminal, or may be the C-RNTI.

Based on the foregoing solution, before the receiving data sent by aterminal, the method further includes: broadcasting configurationinformation, where the configuration information includes at least oneof feedback or retransmission configuration information, physical layerparameter configuration information, non-scheduled transmissionconfiguration information, MAC layer control information, and channelconfiguration information.

The feedback or retransmission configuration information includes atleast one of the following: a hybrid automatic repeat request (HARQ)process number, a retransmission redundancy version, an indication aboutwhether to reset media access control (MAC), a physical downlink controlchannel (PDCCH) time-frequency resource used for feedback or downlinkdata sending, a timing relationship from uplink sending to downlinkfeedback, and a timing relationship from downlink sending to uplinkfeedback.

The physical layer parameter configuration information includes at leastone of the following: transmission time interval (TTI) duration, acyclic prefix (CP) length, a subcarrier spacing, and a physical channeltype.

The non-scheduled transmission configuration information includes atleast one of the following: a quantity of times of non-scheduled uplinkblind retransmission, a non-scheduled automatic retransmission interval,non-scheduled transmission signal received power expected by a basestation, a non-scheduled transmission power boost step, a demodulationreference signal DRMS list available for non-scheduled transmission, anda modulation and coding scheme (MCS) available for non-scheduledtransmission.

The MAC layer control information includes at least one of thefollowing: whether to report channel state information (CSI), periodicor aperiodic CSI reporting, a CSI reporting class, whether to report apower headroom report (PHR), periodic or aperiodic PHR reporting,whether to report a buffer status report (BSR), a BSR reporting format,and periodic or aperiodic BSR reporting.

The channel configuration information includes at least one of thefollowing: a radio link control (RLC) configuration corresponding to aservice channel, a correspondence between a service channel and a flowidentifier, and an RLC configuration corresponding to a control channel.

In the foregoing solution, when an RLC layer is maintained by the anchorbase station, the configuration information does not include the channelconfiguration information.

In a specific implementation, the data sent by the serving base stationto the anchor base station is RLC data or MAC data.

A meaning of this solution is as follows: The serving base station maybe responsible for maintaining a physical layer, a MAC layer, and theRLC layer, and the anchor base station maintains a packet dataconvergence protocol (PDCP) layer; in this case, the data sent by theserving base station to the anchor base station is the RLC data.Alternatively, the serving base station may be responsible formaintaining a physical layer and a MAC layer, and the anchor basestation maintains the RLC layer and a PDCP layer; in this case, the datasent by the serving base station to the anchor base station is the MACdata.

In a specific implementation, the data further includes key updateindication information sent by the terminal, where the key updateindication information may include a simple key change indication or aspecific key deduction parameter.

In this solution, if a key previously used by the terminal needs to bechanged, the serving base station and the anchor base station need toobtain a deduction parameter used by the terminal to change the key. Aspecific manner may be as follows: The terminal sends the deductionparameter, or the deduction parameter is obtained based on preconfiguredinformation, or the anchor base station or the serving base stationsends the deduction parameter to the terminal.

In a specific implementation, the method further includes: allocatingnew terminal identification information to the terminal; and sending thenew terminal identification information to the terminal, and/or sendingthe new terminal identification information to the anchor base station.

In a specific implementation, the method further includes: starting atimer after the data is received, and deleting the identificationinformation of the terminal after the timer expires.

In a specific implementation, the method further includes: sending aterminal identity deletion instruction to the anchor base station, toinstruct the anchor base station to delete the identificationinformation of the terminal.

In the foregoing solution, the serving base station may allocate the newterminal identification information to the terminal or delete theidentification information of the terminal. In both of the processes,the anchor base station needs to be instructed to perform acorresponding update.

In a specific implementation, the method further includes: establishinga MAC entity or an RLC entity corresponding to the terminal; orreceiving configuration information and/or state information, sent bythe anchor base station, of an RLC entity corresponding to the terminal.

In this solution, the MAC entity or the RLC entity corresponding to theterminal is usually established after a conflict is resolved, or afterthe anchor base station successfully receives the data, or after theuplink data of the terminal is successfully sent and an acknowledgementmessage is returned to the terminal.

According to a second aspect of the embodiments of this application, adata transmission method is provided. The method includes: obtaining, bya terminal in an inactive state, configuration information used for datasending. The method also includes sending, by the terminal, data to aserving base station based on the configuration information, where thedata includes to-be-sent data and identification information of theterminal.

This solution is performed by the terminal. When the terminal needs tosend uplink data, the terminal sends the to-be-sent data together withthe identification information of the terminal to the serving basestation based on preconfigured configuration information or receivedconfiguration information broadcast by the serving base station, andsends the data to an anchor base station of the terminal by using theserving base station, so as to implement uplink data transmission.Neither context migration nor switching of a link between a core networkand a base station needs to be performed. Therefore, interface resourcesare saved, and transmission efficiency is improved.

In a specific implementation, the method further includes the followingimplementations.

In an implementation, when the terminal enters the inactive state froman active state, a PDCP entity and an RLC entity of each logical channelare stored, and a MAC entity and/or a physical channel configurationare/is reset; or when the terminal enters the inactive state from anactive state, a packet data convergence protocol PDCP entity is storedor configured, and an RLC entity and/or a MAC entity and/or a physicalchannel configuration are/is reset.

Specifically, state information and configuration information of PDCPand RLC are stored.

In an implementation, when the terminal enters the inactive state froman active state, security contexts such as an SN number, an HFN, and akey of PDCP are stored, and an RLC entity and/or a MAC entity and/or aphysical channel configuration are/is reset. In a specificimplementation, a PDCP entity corresponding to the broadcast logicalchannel is configured.

In a specific implementation, the identification information of theterminal includes: a unique identifier used to indicate the terminal inan access-network notification area in which the terminal is located; ora C-RNTI; or an identifier allocated by a core-network device.

In this solution, the identification information may further includeinformation used to indicate the anchor base station to which theterminal belongs.

In a specific implementation, the obtaining configuration informationused for data sending includes: obtaining the configuration informationpreconfigured in a protocol; or receiving the configuration informationbroadcast by the serving base station or sent by the anchor basestation, where the configuration information includes at least one offeedback or retransmission configuration information, physical layerparameter configuration information, non-scheduled transmissionconfiguration information, MAC layer control information, and channelconfiguration information.

The feedback or retransmission configuration information includes atleast one of the following: a HARQ process number, a retransmissionredundancy version, an indication about whether to reset MAC, a PDCCHtime-frequency resource used for feedback or downlink data sending, atiming relationship from uplink sending to downlink feedback, and atiming relationship from downlink sending to uplink feedback.

The physical layer parameter configuration information includes at leastone of the following: TTI duration, a CP length, a subcarrier spacing,and a physical channel type.

The non-scheduled transmission configuration information includes atleast one of the following: a quantity of times of non-scheduled uplinkblind retransmission, a non-scheduled automatic retransmission interval,non-scheduled transmission signal received power expected by a basestation, a non-scheduled transmission power boost step, a DRMS listavailable for non-scheduled transmission, and an MCS available fornon-scheduled transmission.

The MAC layer control information includes at least one of thefollowing: whether to report CSI, periodic or aperiodic CSI reporting, aCSI reporting class, whether to report a PHR, periodic or aperiodic PHRreporting, whether to report a BSR, a BSR reporting format, and periodicor aperiodic BSR reporting.

The channel configuration information includes at least one of thefollowing: an RLC configuration corresponding to a service channel, acorrespondence between a service channel and a flow identifier, and anRLC configuration corresponding to a control channel.

In a specific implementation, before the sending data to a serving basestation based on the configuration information, the method furtherincludes: obtaining the to-be-sent data; and performing encryptionand/or integrity protection on the to-be-sent data by using apre-obtained key or a key currently obtained through calculation.

In a specific implementation, before the obtaining the to-be-sent data,the method further includes: receiving indication information sent bythe anchor base station, where the indication information is used toindicate whether the terminal needs to update a key; and if theindication information indicates that the terminal does not need tochange the key, determining that the key obtained last time can still beused.

In a specific implementation of this solution, the method furtherincludes: if the indication information indicates that the terminalneeds to update the key, obtaining a new key by performing deduction byusing a deduction parameter received last time; and sending key updateindication information to the serving base station, where the key updateindication information may include the deduction parameter.

In another specific implementation, the method further includes:obtaining new terminal identification information allocated by theserving base station.

According to a third aspect of the embodiments of this application, adata transmission method is provided. The method includes receiving, byan anchor base station, data sent by a serving base station, where thedata includes to-be-sent data sent by a terminal and identificationinformation of the terminal. The method also includes obtaining, by theanchor base station based on the identification information of theterminal, link information corresponding to the terminal. The methodalso includes sending, by the anchor base station, the data to acore-network device based on the link information.

This solution is performed by the anchor base station of the terminal,that is, a base station to which the terminal is connected last time fordata transmission. Uplink data of the terminal is forwarded to theanchor base station by using the serving base station and through aninteraction between the anchor base station and the serving base stationthat currently provides an air interface resource for the terminal, andis then transmitted to a core network. Neither context migration norswitching between the core network and a base station needs to beperformed. Therefore, signaling and interface overheads are reduced, anddata transmission efficiency is improved.

In a specific implementation, the method further includes: receiving anIP flow identifier and/or a logical channel identifier and/or a channeltype that are/is corresponding to the to-be-sent data and that are/issent by the serving base station, where the logical channel identifieris included in the data or not included in the data.

In a specific implementation, the method further includes: receiving newterminal identification information of the terminal that is sent by theserving base station.

In a specific implementation, the method further includes: receiving aterminal identity deletion instruction sent by the serving base station;and deleting the identification information of the terminal according tothe terminal identity deletion instruction.

In a specific implementation, the method further includes: sending, tothe serving base station, configuration information and/or stateinformation of an RLC entity corresponding to the terminal.

According to a fourth aspect of the embodiments of this application, adata transmission method is provided. The method includes receiving, bya serving base station, data sent by an anchor base station, where thedata includes to-be-sent data that is to be sent to a terminal andidentification information of the terminal. The method also includessending, by the serving base station, the to-be-sent data to theterminal.

In a specific implementation, the identification information includes:information about a unique identifier used to indicate the terminal inan access-network notification area in which the terminal is located, ora C-RNTI allocated to the terminal, or an identifier allocated by acore-network device to the terminal.

This solution is performed by the serving base station. Downlink datatransmission of the terminal is implemented through an interactionbetween the serving base station and the anchor base station. Theserving base station does not need to establish a link to thecore-network device, but directly receives, by using the anchor basestation, downlink data that is sent by the core-network device by usingthe anchor base station, and forwards the downlink data to the terminalbased on the identification information of the terminal. Therefore,interface resources are saved, and signaling overheads are reduced.

According to a fifth aspect of the embodiments of this application, adata transmission method is provided. The method includes receiving, byan anchor base station, data sent by a core-network device, where thedata includes to-be-sent data that is to be sent to a terminal andidentification information of the terminal. The method also includesdetermining, by the anchor base station, a serving base station of theterminal based on the identification information of the terminal. Themethod also includes sending, by the anchor base station, the data tothe serving base station.

In a specific implementation, the identification information includes:information about a unique identifier used to indicate the terminal inan access-network notification area in which the terminal is located, ora C-RNTI allocated to the terminal.

This solution is performed by the anchor base station. The anchor basestation directly forwards, to the serving base station, downlink datasent by a core network, so that the serving base station forwards thedownlink data to the terminal. In this process, neither contextmigration nor switching of a link between the core network and a basestation needs to be performed. Therefore, interface resources are saved,and signaling overheads are reduced.

According to a sixth aspect of the embodiments of this application, adata transmission apparatus is provided. The apparatus includes areceiving module, configured to receive data sent by a terminal in aninactive state, where the data includes to-be-sent data sent by theterminal and identification information of the terminal. The apparatusalso includes a processing module, configured to determine an anchorbase station of the terminal based on the identification information.The apparatus also includes a sending module, configured to send thedata to the anchor base station.

In a specific implementation, the receiving module is further configuredto receive a logical channel identifier corresponding to the data sentby the terminal; and the sending module is further configured to send,to the anchor base station, an IP flow identifier and/or a logicalchannel identifier and/or a channel type corresponding to the to-be-sentdata, where the logical channel identifier is included in the data ornot included in the data.

In a specific implementation, the identification information received bythe receiving module includes: a unique identifier used to indicate theterminal in an access-network notification area in which the terminal islocated; or a C-RNTI; or an identifier allocated by a core-networkdevice.

In a specific implementation, the sending module is further configuredto broadcast configuration information: at least one of feedback orretransmission configuration information, physical layer parameterconfiguration information, non-scheduled transmission configurationinformation, MAC layer control information, and channel configurationinformation.

The feedback or retransmission configuration information includes atleast one of the following: a HARQ process number, a retransmissionredundancy version, an indication about whether to reset MAC, a PDCCHtime-frequency resource used for feedback or downlink data sending, atiming relationship from uplink sending to downlink feedback, and atiming relationship from downlink sending to uplink feedback.

The physical layer parameter configuration information includes at leastone of the following: TTI duration, a CP length, a subcarrier spacing,and a physical channel type.

The non-scheduled transmission configuration information includes atleast one of the following: a quantity of times of non-scheduled uplinkblind retransmission, a non-scheduled automatic retransmission interval,non-scheduled transmission signal received power expected by a basestation, a non-scheduled transmission power boost step, a DRMS listavailable for non-scheduled transmission, and an MCS available fornon-scheduled transmission.

The MAC layer control information includes at least one of thefollowing: whether to report CSI, periodic or aperiodic CSI reporting, aCSI reporting class, whether to report a PHR, periodic or aperiodic PHRreporting, whether to report a BSR, a BSR reporting format, and periodicor aperiodic BSR reporting.

The channel configuration information includes at least one of thefollowing: an RLC configuration corresponding to a service channel, acorrespondence between a service channel and a flow identifier, and anRLC configuration corresponding to a control channel.

In a specific implementation, the to-be-sent data received by thereceiving module is RLC data or MAC data.

In a specific implementation, the data further includes key updateindication information sent by the terminal. The key update indicationinformation in this solution may include a deduction parameter.

In a specific implementation, the processing module is furtherconfigured to allocate new terminal identification information to theterminal; and the sending module is further configured to send the newterminal identification information to the terminal, and/or send the newterminal identification information to the anchor base station.

In a specific implementation, the processing module is furtherconfigured to start a timer after the data is received, and delete theidentification information of the terminal after the timer expires.

In a specific implementation, the sending module is further configuredto send a terminal identity deletion instruction to the anchor basestation, to instruct the anchor base station to delete theidentification information of the terminal.

In a specific implementation, the processing module is furtherconfigured to establish a MAC entity or an RLC entity corresponding tothe terminal; or the receiving module is further configured to receiveconfiguration information and/or state information, sent by the anchorbase station, of an RLC entity corresponding to the terminal.

According to a seventh aspect of the embodiments of this application, adata transmission apparatus is provided. The apparatus includes aprocessing module, configured to obtain configuration information usedfor data sending. The apparatus also includes a sending module,configured to send data to a serving base station based on theconfiguration information, where the data includes to-be-sent data andidentification information.

In a specific implementation, the processing module is specificallyconfigured to: when the apparatus enters an inactive state from anactive state, store a PDCP entity and an RLC entity of each logicalchannel, and reset a MAC entity and/or a physical channel configuration;or when the apparatus enters an inactive state from an active state,store or configure a PDCP entity, and reset an RLC entity and/or a MACentity and/or a physical channel configuration.

In a specific implementation, the identification information of theterminal includes: a unique identifier used to indicate the terminal inan access-network notification area in which the terminal is located; ora C-RNTI; or an identifier allocated by a core-network device.

In a specific implementation, the processing module is furtherconfigured to obtain the configuration information preconfigured in aprotocol; or the receiving module is further configured to receive theconfiguration information broadcast by the serving base station or sentby an anchor base station, where the configuration information includesat least one of feedback or retransmission configuration information,physical layer parameter configuration information, non-scheduledtransmission configuration information, MAC layer control information,and channel configuration information.

The feedback or retransmission configuration information includes atleast one of the following: a HARQ process number, a retransmissionredundancy version, an indication about whether to reset MAC, a PDCCHtime-frequency resource used for feedback or downlink data sending, atiming relationship from uplink sending to downlink feedback, and atiming relationship from downlink sending to uplink feedback.

The physical layer parameter configuration information includes at leastone of the following: transmission time interval TTI duration, a cyclicprefix CP length, a subcarrier spacing, and a physical channel type.

The non-scheduled transmission configuration information includes atleast one of the following: a quantity of times of non-scheduled uplinkblind retransmission, a non-scheduled automatic retransmission interval,non-scheduled transmission signal received power expected by a basestation, a non-scheduled transmission power boost step, a DRMS listavailable for non-scheduled transmission, and an MCS available fornon-scheduled transmission.

The MAC layer control information includes at least one of thefollowing: whether to report CSI, periodic or aperiodic CSI reporting, aCSI reporting class, whether to report a PHR, periodic or aperiodic PHRreporting, whether to report a BSR, a BSR reporting format, and periodicor aperiodic BSR reporting.

The channel configuration information includes at least one of thefollowing: an RLC configuration corresponding to a service channel, acorrespondence between a service channel and a flow identifier, and anRLC configuration corresponding to a control channel.

In a specific implementation, before the data is sent to the servingbase station based on the configuration information, the processingmodule is further configured to: obtain the to-be-sent data; and performencryption and/or integrity protection on the to-be-sent data by using apre-obtained key or a key currently obtained through calculation.

In a specific implementation, before the to-be-sent data is obtained,the receiving module is further configured to receive indicationinformation sent by the anchor base station, where the indicationinformation is used to indicate whether the terminal needs to update akey; and if the indication information indicates that the terminal doesnot need to change the key, the processing module determines that thekey obtained last time can still be used.

In a specific implementation, if the indication information indicatesthat the terminal needs to update the key, the processing module isfurther configured to obtain a new key by performing deduction by usinga deduction parameter received last time; and the sending module isfurther configured to send key update indication information to theserving base station, where the key update indication information mayinclude the deduction parameter.

In a specific implementation, the processing module is furtherconfigured to obtain new terminal identification information allocatedby the serving base station.

According to an eighth aspect of the embodiments of this application, adata transmission apparatus is provided. The apparatus includes areceiving module, configured to receive data sent by a serving basestation, where the data includes to-be-sent data sent by a terminal andidentification information of the terminal. The apparatus also includesa processing module, configured to obtain, based on the identificationinformation of the terminal, link information corresponding to theterminal; and a sending module, configured to send the data to acore-network device based on the link information.

In a specific implementation, the receiving module is further configuredto receive an IP flow identifier and/or a logical channel identifierand/or a channel type that are/is corresponding to the to-be-sent dataand that are/is sent by the serving base station, where the logicalchannel identifier is included in the data or not included in the data.

In a specific implementation, the receiving module is further configuredto receive new terminal identification information of the terminal thatis sent by the serving base station.

In a specific implementation, the receiving module is further configuredto receive a terminal identity deletion instruction sent by the servingbase station; and the processing module is further configured to deletethe identification information of the terminal according to the terminalidentity deletion instruction.

In a specific implementation, the sending module is further configuredto send, to the serving base station, configuration information and/orstate information of an RLC entity corresponding to the terminal.

According to a ninth aspect of the embodiments of this application, adata transmission apparatus is provided. The apparatus includes areceiving module, configured to receive data sent by an anchor basestation, where the data includes to-be-sent data that is to be sent to aterminal and identification information of the terminal. The apparatusalso includes a sending module, configured to send the to-be-sent datato the terminal based on the identification information of the terminal.

According to a tenth aspect of the embodiments of this application, adata transmission apparatus is provided. The apparatus includes areceiving module, configured to receive data sent by a core-networkdevice, where the data includes to-be-sent data that is to be sent to aterminal and identification information of the terminal. The apparatusalso includes a processing module, configured to determine a servingbase station of the terminal based on the identification information ofthe terminal. The apparatus also includes a sending module, configuredto send the data to the serving base station.

According to an eleventh aspect of the embodiments of this application,a base station is provided. The base station provides an air interfacefor a terminal, and the base station may interact with another basestation. The base station includes at least one processor, a memory, anda communications interface (for example, a receiver and a transmitter).The at least one processor, the memory, and the communications interfaceare connected to each other by using a bus. The memory stores a computerexecutable instruction. The at least one processor executes the computerexecutable instruction stored in the memory, so that the base stationperforms the data transmission method according to any one of the firstaspect or the implementations of the first aspect or any one of thefifth aspect or the implementations of the fifth aspect by exchangingdata with another base station and a terminal through the communicationsinterface.

According to a twelfth aspect of the embodiments of this application, aterminal is provided. The terminal includes at least one processor, amemory, and a communications interface (for example, the terminaltransmits data by using a receiver and a transmitter). The at least oneprocessor, the memory, and the communications interface are connected toeach other by using a bus. The memory stores a computer executableinstruction. The at least one processor executes the computer executableinstruction stored in the memory, so that the terminal performs the datatransmission method according to any one of the second aspect or theimplementations of the second aspect by exchanging data with a servingbase station or an anchor base station through the communicationsinterface.

According to a thirteenth aspect of the embodiments of this application,a base station is provided. The base station may interact with anotherbase station, and includes at least one processor, a memory, and acommunications interface (for example, the base station transmits databy using a receiver and a transmitter). The at least one processor, thememory, and the communications interface are connected to each other byusing a bus. The memory stores a computer executable instruction. The atleast one processor executes the computer executable instruction storedin the memory, so that the base station performs the data transmissionmethod according to any one of the third aspect or the implementationsof the third aspect or any one of the fourth aspect or theimplementations of the fourth aspect by exchanging data with anotherbase station or a terminal through the communications interface.

According to a fourteenth aspect of the embodiments of this application,a computer readable storage medium is provided. The computer readablestorage medium stores a computer executable instruction. When at leastone processor of a base station executes the computer executableinstruction, the base station performs the data transmission methodaccording to any one of the first aspect or the implementations of thefirst aspect or any one of the fifth aspect or the implementations ofthe fifth aspect.

According to a fifteenth aspect of the embodiments of this application,a computer readable storage medium is provided. The computer readablestorage medium stores a computer executable instruction. When at leastone processor of a terminal executes the computer executableinstruction, the terminal performs the data transmission methodaccording to any one of the second aspect or the implementations of thesecond aspect.

According to a sixteenth aspect of the embodiments of this application,a computer readable storage medium is provided. The computer readablestorage medium stores a computer executable instruction. When at leastone processor of a base station executes the computer executableinstruction, the base station performs the data transmission methodaccording to any one of the third aspect or the implementations of thethird aspect or any one of the fourth aspect or the implementations ofthe fourth aspect.

According to a seventeenth aspect of the embodiments of thisapplication, a computer program product is provided. The computerprogram product includes a computer executable instruction. The computerexecutable instruction is stored in a computer readable storage medium.At least one processor of a base station may read the computerexecutable instruction from the computer readable storage medium, andthe at least one processor executes the computer executable instruction,so that the base station implements the data transmission methodaccording to any one of the first aspect or the implementations of thefirst aspect or any one of the fifth aspect or the implementations ofthe fifth aspect.

According to an eighteenth aspect of the embodiments of thisapplication, a computer program product is provided. The computerprogram product includes a computer executable instruction. The computerexecutable instruction is stored in a computer readable storage medium.At least one processor of a terminal may read the computer executableinstruction from the computer readable storage medium, and the at leastone processor executes the computer executable instruction, so that theterminal implements the data transmission method according to any one ofthe second aspect or the implementations of the second aspect.

According to a nineteenth aspect of the embodiments of this application,a computer program product is provided. The computer program productincludes a computer executable instruction. The computer executableinstruction is stored in a computer readable storage medium. At leastone processor of a base station may read the computer executableinstruction from the computer readable storage medium, and the at leastone processor executes the computer executable instruction, so that thebase station implements the data transmission method according to anyone of the third aspect or the implementations of the third aspect orany one of the fourth aspect or the implementations of the fourthaspect.

According to the data transmission method and apparatus provided in theembodiments of this application, when the terminal in the inactive stateneeds to send data, the terminal sends the data and an identity of theterminal to the serving base station that provides an interface. Uplinkdata of the terminal is forwarded to the anchor base station by usingthe serving base station and through an interaction between the anchorbase station and the serving base station that currently provides theair interface resource for the terminal, and is then transmitted to thecore network. Neither context migration nor switching between the corenetwork and the base station needs to be performed. Therefore, signalingand interface overheads are reduced, and data transmission efficiency isimproved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a tracking area update of UE data;

FIG. 2 is a schematic diagram of an application architecture of a datatransmission method according to an embodiment of this application;

FIG. 3 is a schematic flowchart of Embodiment 1 of a data transmissionmethod according to an embodiment of this application;

FIG. 4 is a schematic flowchart of Embodiment 2 of a data transmissionmethod according to an embodiment of this application;

FIG. 5 is a schematic diagram of a design of an anchor base station anda serving base station in a data transmission method according to anembodiment of this application;

FIG. 6 is a schematic diagram of another design of an anchor basestation and a serving base station in a data transmission methodaccording to an embodiment of this application;

FIG. 7 is a schematic structural diagram of Embodiment 1 of a datatransmission apparatus according to an embodiment of this application;

FIG. 8 is a schematic structural diagram of Embodiment 2 of a datatransmission apparatus according to an embodiment of this application;

FIG. 9 is a schematic structural diagram of Embodiment 3 of a datatransmission apparatus according to an embodiment of this application;

FIG. 10 is a schematic structural diagram of Embodiment 4 of a datatransmission apparatus according to an embodiment of this application;and

FIG. 11 is a schematic structural diagram of Embodiment 5 of a datatransmission apparatus according to an embodiment of this application.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Each time a serving base station of a terminal changes, contextmigration needs to be performed, switching of a connection between acore network and a base station needs to be implemented during datatransmission, and an anchor base station needs to be changed. Change ofthe anchor base station results in a terminal key update and contextobtaining. This causes relatively high signaling overheads. In addition,when the terminal moves between two base stations, a context of theterminal is frequently migrated between the two base stations, andinterface overheads between the base stations and the core network andair-interface radio resource control (RRC) signaling overheads are high.To resolve the foregoing problems, embodiments of this applicationpropose a data transmission method. When a terminal is in an inactivestate, uplink data of the terminal or downlink data for the terminal istransmitted through an interaction between a serving base station and ananchor base station, with no need of switching of a link between a corenetwork and a base station. Therefore, interface and signaling overheadsare reduced.

FIG. 2 is a schematic diagram of an application architecture of a datatransmission method according to an embodiment of this application. Asshown in FIG. 2, a terminal is used as an example. The terminal may moveback and forth between tracking areas of a plurality of base stations(also referred to as cells, radio access network nodes, or the like). Inthis solution, the data transmission method provided in this embodimentof this application is described by using, as an example, an anchor basestation to which the terminal is connected when the terminal is in anactive state and a serving base station providing an interface for theterminal after the terminal moves.

FIG. 3 is a schematic flowchart of Embodiment 1 of a data transmissionmethod according to an embodiment of this application. As shown in FIG.3, based on the schematic diagram of application shown in FIG. 2, themethod for transmitting uplink data of a terminal in an inactive statemay specifically include the following steps.

S101. Obtain configuration information used for data sending.

This step is performed by the terminal. The terminal is a user-sidedevice that needs to perform uplink/downlink data exchange, for example,a mobile phone or a tablet computer. When the terminal in the inactivestate needs to send uplink data, the terminal may obtain theconfiguration information used for data sending.

A specific obtaining manner includes at least one of the following.

In a first manner, the terminal receives the configuration informationbroadcast by a serving base station.

In a second manner, the terminal obtains the configuration informationpreconfigured in a protocol, in other words, obtains the configurationinformation from the protocol.

In a third manner, the terminal receives the configuration informationsent by an anchor base station.

In a fourth manner, when the terminal enters the inactive state from anactive state, the terminal stores a packet data convergence protocol(PDCP) entity and a radio link control (RLC) entity of each logicalchannel, and resets a MAC entity and/or a physical channelconfiguration. The terminal may directly obtain the locally storedconfiguration information. The PDCP entity and the RLC entity include aPDCP entity context and an RLC entity context, respectively. The MACentity includes a MAC entity context.

In a fifth manner, when the terminal enters the inactive state from anactive state, the terminal stores a packet data convergence protocol(PDCP) entity and context, and resets a radio link control (RLC) entityand context and/or a MAC entity and/or a physical channel configuration.The terminal directly obtains the locally stored configurationinformation.

In a sixth manner, when the terminal enters the inactive state from anactive state, the terminal stores or configures a packet dataconvergence protocol PDCP entity, and resets an RLC entity and/or a MACentity and/or a physical channel configuration. The PDCP entity includesa PDCP entity context. The MAC entity includes a MAC entity context.

In any one of the foregoing implementations, the configurationinformation includes at least one of feedback or retransmissionconfiguration information, physical layer parameter configurationinformation, non-scheduled transmission configuration information, MAClayer control information, and channel configuration information.

The feedback or retransmission configuration information includes atleast one of the following: a hybrid automatic repeat request (HARQ)process number, a retransmission redundancy version, an indication aboutwhether to reset media access control (MAC), a physical downlink controlchannel (PDCCH) time-frequency resource used for feedback or downlinkdata sending, a timing relationship from uplink sending to downlinkfeedback, and a timing relationship from downlink sending to uplinkfeedback. In the indication about whether to reset MAC, the resettingmeans releasing or zeroing out stored MAC layer configurationinformation, for example, releasing a channel corresponding to a MAClayer, or zeroing a MAC-layer timer. In addition, RLC resetting is alsomentioned in this specification, and means, for example, releasing achannel corresponding to an RLC layer, zeroing an RLC-layer timer, orzeroing a sequence number SN of RLC.

The physical layer parameter configuration information includes at leastone of the following: transmission time interval (TTI) duration, acyclic prefix (CP), a subcarrier spacing, and a physical channel type.

The non-scheduled transmission configuration information includes atleast one of the following: a quantity of times of non-scheduled uplinkblind retransmission, a non-scheduled automatic retransmission interval,non-scheduled transmission signal received power expected by a basestation, a non-scheduled transmission power boost step, a demodulationreference signal DRMS list available for non-scheduled transmission, anda modulation and coding scheme (MCS) available for non-scheduledtransmission. The non-scheduled transmission configuration informationmay further include non-scheduled transmission configurationinformation. In this solution, the non-scheduled transmission means thatthe terminal directly performs one or more times of uplink sending afterobtaining an uplink sending resource by using a broadcast message; orthe terminal performs one or more times of uplink sending afterobtaining an uplink sending resource by using a dedicated message.

The MAC layer control information includes at least one of thefollowing: whether to report channel state information (CSI), periodicor aperiodic CSI reporting, a CSI reporting class, whether to report apower headroom report (PHR), periodic or aperiodic PHR reporting,whether to report a buffer status report (BSR), a BSR reporting format,and periodic or aperiodic BSR reporting.

The channel configuration information includes at least one of thefollowing: an RLC configuration corresponding to a service channel, acorrespondence between a service channel and a flow identifier, and anRLC configuration corresponding to a control channel.

The configuration information further includes identificationinformation of the terminal. The terminal (namely, UE) is used as anexample in the following descriptions. For example, the identificationinformation of the terminal may be an RNA UE ID, a resume ID, a C-RNTI,or terminal identification information allocated by a core network. Theidentification information of the terminal may be allocated or sent bythe anchor base station or the serving base station.

S102. Send data to a serving base station based on the configurationinformation, where the data includes to-be-sent data and identificationinformation.

In this step, after obtaining the configuration information, theterminal sends the uplink data based on the configuration information,and places the to-be-sent data and the identification information of theterminal into the same data for sending. The identification informationof the terminal may be a unique identifier used to indicate the terminalin an access-network notification area in which the terminal is located,or a cell radio network temporary identifier (C-RNTI), or an identifierallocated by a core-network device.

The identification information of the terminal may be allocated by theanchor base station to the terminal, may be allocated by thecore-network device, or may be allocated by the serving base station tothe terminal. This is not limited in this solution.

In a specific implementation of this solution, when the terminal is inthe inactive state (namely, the inactive state), the followingidentifiers may exist: the radio access network notification area (RANNotification Area, RNA) UE ID and the C-RNTI. The RNA UE ID identifies abase station to which the terminal belongs, and is a unique identity ofthe terminal under the base station. Optionally, a network allocates theC-RNTI to the terminal. When an RNA is a single cell, the C-RNTI ispreferentially allocated to the terminal. The RNA UE ID indicatesinformation about an anchor base station that allocates the ID, andfurther indicates unique terminal identification information of theterminal under the base station.

Optionally, when the terminal performs sending by using the C-RNTI orthe identifier allocated by the core network, the terminal sendsinformation about a cell, a base station, or an RNA that allocates theC-RNTI. The serving base station may determine the anchor base stationbased on the information about the cell, the base station, or the RNA,for example, through network management configuration.

Optionally, the inactive state may further include an idle state in LTE.In this case, some or all configuration parameters in a connected stateare stored. In this case, a UE ID may be a resume ID.

After obtaining the configuration information, the terminal encrypts theto-be-sent data by using a pre-obtained key or a key obtained throughcalculation, to obtain data, and sends the data together with theidentification information of the terminal or other signaling to theserving base station.

In addition, the terminal may further send, to the serving base station,a logical channel identifier corresponding to the data. The logicalchannel identifier may be carried in the data or not carried in thedata.

The serving base station receives the data sent by the terminal, wherethe data carries at least the data sent by the terminal and theidentification information of the terminal.

S103. Determine an anchor base station of a terminal based on theidentification information.

This step is performed by the serving base station of the terminal. Theserving base station provides an air interface for the terminal. Afterreceiving the data sent by the terminal, the serving base stationdetermines the anchor base station of the terminal based on theidentification information of the terminal in the data, so as totransmit the uplink data of the terminal to the core-network device byusing the anchor base station of the terminal.

In a specific implementation of this solution, the serving base stationmay allocate or release the identification information of the terminal.The C-RNTI is used as an example. Occasions for allocating the C-RNTI tothe terminal include: during data transmission (random access channel(RACH) data transmission or contention-based data transmission), aftercell reselection, when the terminal enters the inactive state from theactive state, when an RNA location update notification is received, andthe like. Optionally, the C-RNTI is retained for a period of time. TheRNA location update notification means that the terminal notifies, whena RNA changes, the base station of an RNA in which the terminal islocated; or periodically notifies the base station of an RNA in whichthe terminal is located.

For example, when the RNA changes or the anchor base station of theterminal changes, a new anchor base station allocates an RNA ID or aresume ID, and notifies the terminal of the RNA ID or the resume ID.

Optionally, after allocating new terminal identification information(for example, a C-RNTI) to the terminal, the serving base stationnotifies the anchor base station of the new terminal identificationinformation, in other words, the serving base station allocates the newterminal identification information to the terminal, and sends the newterminal identification information to the anchor base station.

An occasion for releasing the C-RNTI of the terminal includes: releasingthe C-RNTI of the terminal in an implicit or explicit manner. The C-RNTImay be synchronously released by using an inactive timer or L2/L1signaling. Alternatively, the C-RNTI is released only when the terminalenters the idle state or sends uplink data in another cell. To bespecific, the serving base station starts a timer after receiving thedata, and deletes the identification information of the terminal afterthe timer expires, and may send a terminal identity deletion instructionto the anchor base station, to instruct the anchor base station todelete the identification information of the terminal. In this solution,if the anchor base station does not participate in terminal identitymanagement, the serving base station does not need to notify the anchorbase station when releasing the identification information of theterminal.

In an optional implementation solution, the anchor base stationmaintains the C-RNTI based on an inactive timer. For example, the anchorbase station starts the inactive timer after receiving uplink ordownlink data, and deletes the identification information of theterminal after the timer expires.

S104. Send the data to the anchor base station.

In this step, the serving base station sends the data to the anchor basestation of the terminal.

The data may include complete or partial RLC data received from theterminal, or complete or partial MAC data received from the terminal.

After demultiplexing the received data, the serving base station furtherneeds to send an IP flow identifier and/or a logical channel identifierand/or a logical channel type to the anchor base station.

When there is no one-to-one mapping relationship between a logicalchannel and an IP flow or a radio access bearer, IP flow informationfurther needs to be sent to the anchor base station. The IP flowinformation may be in a MAC layer protocol unit, an RLC layer protocolunit, or a PDCP layer protocol unit sent by the terminal.

In addition, the serving base station may further send, to the anchorbase station, a logical channel and/or a channel type corresponding tothe data sent by the terminal. Likewise, the logical channel is includedin or not included in data obtained through processing by the servingbase station.

When the RLC entity is on the anchor base station, the serving basestation sends a MAC packet to the anchor base station; or when the RLCentity is on the serving base station, the serving base station sends anRLC packet to the anchor base station. The MAC packet and the RLC packetmay not include logical channel information.

In an optional implementation, when a base-station-level transmissionlink is established between the serving base station and the anchor basestation, the terminal needs to send the C-RNTI and a cell identifier tothe anchor base station. When a cell-level common transmission link isestablished between the serving base station and the anchor basestation, the serving base station sends the C-RNTI to the anchor basestation through the link. When a dedicated terminal link is establishedbetween the serving base station and the anchor base station, theterminal does not need to send any terminal ID to the anchor basestation.

In an optional implementation, when the RNA UE ID or the resume ID issent between the serving base station and the anchor base station, acommon or dedicated bearer between the serving base station and theanchor base station may be used.

In an optional implementation, considering that a small amount of datais transmitted without state switching and a large amount of data istransmitted with state switching, the terminal may determine ato-be-used manner based on an amount of to-be-sent data, or the servingbase station determines, based on a BSR status in non-scheduled data,whether to perform migration from the anchor base station to the servingbase station or switch the terminal to an active connected state.

S105. Obtain, based on the identification information of the terminal,link information corresponding to the terminal.

This step is performed by the anchor base station. After receiving thedata sent by the serving base station, the anchor base station obtains,based on the identification information of the terminal carried in thedata, the link information corresponding to the terminal. Herein, thelink information is information about a link that is established betweenthe anchor base station and the core-network device when the terminaltransmits the data to the anchor base station and that is specially usedto transmit the data of the terminal, for example, IP flow informationor radio access bearer information.

S106. Send the data to a core-network device based on the linkinformation.

In this step, the anchor base station sends the received data to thecore-network device based on the link information corresponding to theterminal, to complete uplink data transmission of the terminal in theinactive state.

In this process, switching of a link between the core-network device anda base station does not need to be performed, and the serving basestation does not need to obtain a context from the anchor base stationof the terminal either, in other words, context migration does not needto be performed.

According to the data transmission method provided in this embodiment,the uplink data of the terminal is forwarded to the anchor base stationby using the serving base station and through an interaction between theanchor base station and the serving base station that currently providesan air interface resource for the terminal, and the anchor base stationsends the data to the core-network device. Neither context migration norswitching between the core network and a base station needs to beperformed. Therefore, signaling and interface overheads are reduced, anddata transmission efficiency is improved.

FIG. 4 is a schematic flowchart of Embodiment 2 of a data transmissionmethod according to an embodiment of this application. As shown in FIG.4, specific steps of transmitting, by a core-network device, downlinkdata to a terminal include the following steps.

S201. An anchor base station receives data sent by the core-networkdevice.

In this step, when or before the core-network device needs to senddownlink data to the terminal, the core-network device sends the data tothe anchor base station through a link that is established between thecore-network device and the anchor base station of the terminal and thatis specially used to transmit terminal data.

When no dedicated bearer is established between the anchor base stationand the core-network device, the data includes the to-be-sent data thatis to be sent by the core-network device to the terminal andidentification information of the terminal, or the core-network devicesends only the data to the anchor base station after receiving a pagingresponse.

In this solution, the core-network device may be a device such as amobility management entity (MME) or a gateway.

S202. Determine a serving base station of the terminal based onidentification information of the terminal.

When the core-network device has established a dedicated bearer, anidentity of the terminal does not need to be obtained in step S202;instead, a user is determined based on dedicated bearer information.

If the anchor base station has no C-RNTI, for example, a C-RNTI hasexpired or has been released, the anchor base station may initiate apaging process, to instruct a nearby base station or the serving basestation to page the terminal. A paging message may be generated by theanchor base station or the serving base station. Some or all parametersfor determining paging, for example, the identity of the terminal or apaging occasion calculation parameter, may be provided by the anchorbase station. After the paging response is received, S203 is performed.

If the anchor base station has a valid C-RNTI of the terminal, S203 isperformed.

In an optional implementation, regardless of whether a C-RNTI exists,the anchor base station sends the data and the identity of the terminalto the serving base station.

S203. Send the data to the serving base station.

The anchor base station determines the serving base station thatcurrently provides an air interface resource for the terminal, and sendsthe received data to the serving base station.

If the anchor base station cannot determine the serving base station towhich the terminal belongs, the serving base station of the terminalnotifies the anchor base station after receiving the paging response.

In an implementation, if there is no terminal-specific transmissionchannel between the anchor base station and the serving base station, anRNA UE identifier or a resume ID identifier is sent to the serving basestation.

In an implementation, the anchor base station may send a valid C-RNTI.If there is no cell-level dedicated transmission channel between theanchor base station and the serving base station, an identifier of aserving cell is further sent, and the information is notified by theserving base station to the anchor base station.

If there is the terminal-specific transmission channel between theanchor base station and the serving base station, the identity of theterminal is not sent to the serving base station.

S204. Send to-be-sent data to the terminal.

In this step, the serving base station receives the data sent by theanchor base station, where the data includes the to-be-sent data that isto be sent to the terminal and the identification information of theterminal; and sends the to-be-sent data to the terminal based on theidentification information of the terminal, to complete downlink datatransmission of the terminal.

In a possible implementation, UE is used as an example. The C-RNTI ofthe terminal is found based on the RNA UE identifier or the resume IDidentifier sent by the anchor base station, and data is sent in a cellin which the terminal is located.

In a possible implementation, based on the RNA UE identifier or theresume ID identifier sent by the anchor base station, data and the IDare added to downlink transmission content, and downlink sending isperformed by using a common RNTI, for example, a P-RNTI, or a commonRNTI allocated to the UE when the UE enters an inactive state.

In a possible implementation, data is sent, based on the C-RNTI sent bythe anchor base station, in a cell in which the terminal is located.

In this solution, similar to that in uplink data information, theidentification information of the terminal includes: information about aunique identifier used to indicate the terminal in an access-networknotification area in which the terminal is located, or the C-RNTIallocated to the terminal.

According to the data transmission method provided in this embodiment,the downlink data transmission of the terminal is implemented through aninteraction between the serving base station and the anchor basestation. The serving base station does not need to establish a link tothe core-network device, but directly receives, by using the anchor basestation, the downlink data sent by the core-network device by using theanchor base station, and forwards the downlink data to the terminalbased on the identification information of the terminal. Therefore,interface resources are saved, and signaling overheads are reduced.

In an implementation process of the data transmission method provided inany one of the foregoing embodiments, the interaction between the anchorbase station and the serving base station may be MAC layer dataexchange, or may be RLC layer data exchange. Uplink data transmission isused as an example. Details are as follows.

FIG. 5 is a schematic diagram of a design of an anchor base station anda serving base station in a data transmission method according to anembodiment of this application. As shown in FIG. 5, the serving basestation may be responsible for maintaining a physical layer, a MAClayer, and an RLC layer; and the anchor base station maintains a packetdata convergence protocol (Packet Data Convergence Protocol, PDCP)layer, and is responsible for security and maintaining a connection to acore-network device. In this case, data sent by the serving base stationto the anchor base station is complete or partial RLC data.

Optionally, some RLC layer functions are configured on the serving basestation, and some RLC functions are configured on the anchor basestation.

The RLC functions include at least one of the following functions: anautomatic repeat request (ARQ) function, segmentation, and re-sorting.

Optionally, a downlink RLC function is configured on the serving basestation, and an uplink RLC function is configured on the anchor basestation.

In an optional implementation, the serving base station is a distributedunit DU, and the anchor base station is a centralized unit CU.

FIG. 6 is a schematic diagram of another design of an anchor basestation and a serving base station in a data transmission methodaccording to an embodiment of this application. As shown in FIG. 6, theserving base station may be alternatively responsible for maintaining aphysical layer and a MAC layer, and the anchor base station maintains anRLC layer and a PDCP layer. In this case, data sent by the serving basestation to the anchor base station is MAC data. This means that theanchor base station maintains the RLC layer and the PDCP layer, and isresponsible for an ARQ, segmentation, and the like, and security, andthe serving base station maintains the physical layer (PHY) and MAC; inthis case, the data sent by the serving base station to the anchor basestation is complete or partial MAC data.

Optionally, in this embodiment of this application, some RLC functionsof the anchor base station may be moved down to MAC, and some RLCfunctions of the anchor base station may be moved up to PDCP of theserving base station.

Configuration management: After a terminal enters an inactive state froman active state, or a cell of the terminal changes, the terminal resetsMAC and the PHY, and maintains, by default, a relationship between RLC,an RB/a logical channel, and a flow identifier (flow ID) that arededicated for the active state. Upon state switching, a network mayinstruct the terminal to delete some bearers.

Data sending: If the cell of the terminal does not change, the terminalsends to-be-sent data and identification information (for example, aC-RNTI). After the cell changes, the terminal sends to-be-sent data andan RNA UE ID/(a C-RNTI and information about a cell that allocates theC-RNTI).

Data transmission between base stations: Data received by the servingbase station includes the to-be-sent data and the identificationinformation of the terminal. The serving base station determines anoriginal gNB, namely, an anchor base station, based on theidentification information of the terminal. After the gNB changes, theserving base station sends, to the anchor base station of the terminal,MAC service data unit (SDU) data and a logical channel/flow ID, namely,an RNA UE ID.

In a specific implementation of this solution, after receiving the datasent by the terminal, the serving base station obtains an RLCconfiguration parameter from the anchor base station, that is, theserving base station receives configuration information and/or stateinformation, sent by the anchor base station, of an RLC entitycorresponding to the terminal, and establishes the RLC entity. After aninactive timer expires, the RLC entity is released. Usually, theinactive timer is started or restarted when uplink or downlink data isreceived.

In an optional implementation, the serving base station mayalternatively establish a MAC entity or an RLC entity corresponding tothe terminal, after a contention-based sending conflict is resolved, forexample, after random access is completed or contention-basednon-scheduled transmission is completed, or when it is determined thatthe anchor base station successfully receives the data, or after uplinkdata of the terminal is successfully sent and an acknowledgement messageis returned to the terminal.

In the foregoing two implementations, if there are a plurality oflogical channels, a plurality of RLC entities corresponding to theplurality of logical channels need to be established; or if there isonly one logical channel, there is only one RLC entity.

When the terminal transmits uplink data on an air interface, the datamay be sent in a contention-based manner, or the data may be sentthrough a RACH. Specifically, contention-based data sending is used asan example. The terminal sends data (including a logical channel, a flowidentifier, and the identification information of the terminal (forexample, the RNA UE ID)) to the serving base station, and receives, fromthe serving base station, feedback information that carries an RNA IDand an allocated C-RNTI (in other words, the terminal obtains newterminal identification information allocated by the serving basestation). The RNA ID may be an original cell ID and a C-RNTI allocatedby an original cell. If mapping between the flow ID and the logicalchannel is determined, the terminal may not send the flow ID.

Optionally, when the terminal has a valid C-RNTI and the terminalfurther performs uplink sending in a cell that allocates the C-RNTI, theC-RNTI is used to replace the RNA UE ID. If the terminal supports aplurality of UE IDs, a type of a sent identifier is indicated. Forexample, whether the RNA UE ID or the C-RNTI is used is indicated.Optionally, an original cell ID and an original C-RNTI of the terminalare used to replace the RNA UE ID. Optionally, after a cell of theterminal changes, RLC, MAC, and the PHY are reset. After an uplinksending conflict is resolved, the base station establishes an RLC entityand a MAC entity.

An uplink data transmission process between the serving base station andthe anchor base station is as follows: The serving base stationdetermines, based on the RNA ID, the anchor base station to which theterminal belongs; and after the anchor base station changes, forwardsRLC SDU data, a logical channel/flow ID, and an RNA UE ID to an anchorbase station. After performing decryption and/or integrity protectionprocessing, the anchor base station forwards service data to acore-network device in a corresponding flow.

A downlink data transmission process between the base stations is asfollows: The anchor base station sends downlink data and theidentification information of the terminal (for example, the C-RNTI, theRAN UE ID, or a resume ID) to the serving base station.

A terminal context update is as follows: The serving base station sendsthe C-RNTI and the RNA UE ID (or the original C-RNTI and the originalcell ID) together with data to the anchor base station. Optionally, theserving base station receives an acknowledgement response.Alternatively, through a signaling interaction between the basestations, the anchor base station is instructed to update a C-RNTIcorresponding to the RNA UE ID and a cell that allocates the C-RNTI.

In the data transmission method provided in any one of the foregoingimplementations, a specific case of interface management between thebase stations is as follows:

A common or dedicated bearer is established between the serving basestation and the anchor base station. The common bearer may be based on acell granularity or a base station granularity. Before data sending,establishment of the common or dedicated bearer is triggered.Establishment of a common bearer based on a cell or a base station maybe triggered before data sending.

Context migration and switching of a connection/bearer between a CN anda base station is as follows: The serving base station determines, basedon a BSR and a network load status, whether to trigger obtaining acontext, switching a connection between the CN and a RAN, and obtainingan update key and a deduction parameter.

When the serving base station (an RNA) is a single cell, thisarchitecture is used, and a C-RNTI is allocated and maintained. If theC-RNTI needs to be released, optionally, the anchor base station and/orthe terminal are/is explicitly instructed to release the C-RNTI.

When the terminal needs to send uplink data or the core-network deviceneeds to send downlink data to the terminal, through an interactionbetween the serving base station and the anchor base station, in uplinktransmission, the serving base station sends data to the core-networkdevice by using the anchor base station, so as to implement uplink datatransmission; and in downlink transmission, the anchor base stationreceives data delivered by the core network, and forwards the data tothe terminal by using the serving base station. In this solution, theinteraction between the serving base station and the anchor base stationmay be RLC data, or may be MAC data. In the uplink transmission process,neither context migration nor switching of a link between the corenetwork and a base station needs to be performed. Therefore, interfaceresources are saved, and transmission efficiency is improved.

Based on the technical solution provided in any one of the foregoingembodiments, uplink data transmission is used as an example. Whensending data, the terminal obtains to-be-sent data, and then performsencryption processing and/or integrity protection on the to-be-sent databy using a pre-obtained key or a key currently obtained throughcalculation. Therefore, the terminal needs to obtain the key. A specificmanner is as follows: After entering the inactive state, the terminalstores a key used in a previous data transmission process, and maydirectly use the key in a subsequent data transmission process in whichthe terminal is in the inactive state, or may obtain a new key byperforming deduction based on a deduction parameter, and instruct a basestation side to update the key.

Specific implementations of determining whether to change a key includethe following.

The terminal receives indication information sent by the anchor basestation, where the indication information is used to indicate whetherthe terminal needs to update a key, and if the indication informationindicates that the terminal does not need to change the key, theterminal determines that the key obtained last time can still be used;or if the indication information indicates that the terminal needs toupdate the key, the terminal obtains a new key by performing deductionby using a deduction parameter received last time; and optionally, theterminal may send key update indication information to the serving basestation, to instruct the serving base station to change the key, wherethe key update indication information may include the deductionparameter used by the terminal to obtain the new key through deduction.

The terminal does not change a key in the following cases: a networknotifies the terminal that a cell in which the terminal is located isCU-DU separated/secure; in this case, the terminal considers that a keyreceived in the cell is secure, and in subsequent uplink sending, theterminal always uses the key for security protection, includingprotection of user-plane or control-plane data; the terminal indicatesto the serving base station that a used key is secure; or the terminalnotifies the serving base station of whether the anchor base station ofthe terminal is CU-DU separated, or notifies the serving base station ofonly information about an original cell, so that the serving basestation can determine whether the terminal needs to change a key; or theserving base station determines that an original cell to which theterminal belongs is CU-DU separated and a key is secure, and thereforedoes not instruct the terminal to change the key.

The terminal changes a key in the following cases (a key is changed eachtime a cell changes; or a cell in which a key is used by the terminallast time is not CU-DU separated, or it is considered that a networkindicates that the cell is insecure): the terminal performs deduction byusing a deduction parameter received last time, and indicates to thenetwork that a key is updated, and optionally, notifies the network ofthe used deduction parameter; or the terminal still uses a key used lasttime, for protection, and notifies the serving base station ofinformation about an anchor cell and that the key is insecure or theanchor cell is not CU-DU separated; and if the network determines thatthe key used by the terminal needs to be updated, the network instructsthe terminal to change the key, for example, instructs the terminal toperform key deduction by using a deduction parameter sent last time; orsends a deduction parameter to the terminal, and the terminal makes anacknowledgement.

In this implementation, if a key of the terminal is secure, the key doesnot need to be updated. This can reduce, to some extent, signalingoverheads caused by a key update of the terminal in the inactive state.

FIG. 7 is a schematic structural diagram of Embodiment 1 of a datatransmission apparatus according to an embodiment of this application.The data transmission apparatus 10 includes: a receiving module 11,configured to receive data sent by a terminal in an inactive state,where the data includes to-be-sent data sent by the terminal andidentification information of the terminal; a processing module 12,configured to determine an anchor base station of the terminal based onthe identification information; and a sending module 13, configured tosend the data to the anchor base station.

The data transmission apparatus provided in this embodiment isconfigured to perform a technical solution on a serving base stationside in a process of the data transmission method provided in any one ofthe foregoing embodiments. An implementation principle and a technicaleffect thereof are similar. Details are not described herein again.

Based on the foregoing embodiment, the receiving module 11 is furtherconfigured to receive a logical channel identifier corresponding to thedata sent by the terminal; and the sending module 13 is furtherconfigured to send, to the anchor base station, a logical channelidentifier and/or a channel type corresponding to the to-be-sent data,where the logical channel identifier is included in the data or notincluded in the data.

In a specific implementation, the identification information received bythe receiving module 11 includes: a unique identifier used to indicatethe terminal in an access-network notification area in which theterminal is located; or a C-RNTI; or an identifier allocated by acore-network device.

In a specific implementation, the sending module 13 is furtherconfigured to broadcast configuration information: at least one offeedback or retransmission configuration information, physical layerparameter configuration information, non-scheduled transmissionconfiguration information, MAC layer control information, and channelconfiguration information.

The feedback or retransmission configuration information includes atleast one of the following: a HARQ process number, a retransmissionredundancy version, an indication about whether to reset MAC, a PDCCHtime-frequency resource used for feedback or downlink data sending, atiming relationship from uplink sending to downlink feedback, and atiming relationship from downlink sending to uplink feedback.

The physical layer parameter configuration information includes at leastone of the following: TTI duration, a CP length, a subcarrier spacing,and a physical channel type.

The non-scheduled transmission configuration information includes atleast one of the following: a quantity of times of non-scheduled uplinkblind retransmission, a non-scheduled automatic retransmission interval,non-scheduled transmission signal received power expected by a basestation, a non-scheduled transmission power boost step, a DRMS listavailable for non-scheduled transmission, and an MCS available fornon-scheduled transmission.

The MAC layer control information includes at least one of thefollowing: whether to report CSI, periodic or aperiodic CSI reporting, aCSI reporting class, whether to report a PHR, periodic or aperiodic PHRreporting, whether to report a BSR, a BSR reporting format, and periodicor aperiodic BSR reporting.

The channel configuration information includes at least one of thefollowing: a radio link control RLC configuration corresponding to aservice channel, a correspondence between a service channel and a flowidentifier, and an RLC configuration corresponding to a control channel.

In a specific implementation, the to-be-sent data received by thereceiving module 11 is RLC data, MAC data, or a part of RLC data or MACdata.

In a specific implementation, the data further includes key updateindication information sent by the terminal, where the key updateindication information may include a deduction parameter.

In a specific implementation, the processing module 12 is furtherconfigured to allocate new terminal identification information to theterminal.

In a specific implementation, the sending module 13 is furtherconfigured to send the new terminal identification information to theterminal, and/or send the new terminal identification information to theanchor base station.

In a specific implementation, the processing module 12 is furtherconfigured to start a timer after the data is received, and delete theidentification information of the terminal after the timer expires.

In a specific implementation, the sending module 13 is furtherconfigured to send a terminal identity deletion instruction to theanchor base station, to instruct the anchor base station to delete theidentification information of the terminal.

In a specific implementation, the processing module 12 is furtherconfigured to establish a MAC entity or an RLC entity corresponding tothe terminal; or the receiving module 11 is further configured toreceive configuration information and/or state information, sent by theanchor base station, of an RLC entity corresponding to the terminal.

The data transmission apparatus provided in any one of the foregoingimplementations is configured to perform a technical solution on aserving base station side in any one of the foregoing methodembodiments. An implementation principle and a technical effect thereofare similar. Details are not described herein again.

FIG. 8 is a schematic structural diagram of Embodiment 2 of a datatransmission apparatus according to an embodiment of this application.The data transmission apparatus 20 includes: a processing module 21,configured to obtain configuration information used for data sending;and a sending module 22, configured to send data to a serving basestation based on the configuration information, where the data includesto-be-sent data and identification information.

The data transmission apparatus provided in this embodiment isconfigured to perform a technical solution on a terminal side in any oneof the foregoing method embodiments. An implementation principle and atechnical effect thereof are similar. Details are not described hereinagain.

Based on the foregoing embodiment, the processing module 21 isspecifically configured to: when the apparatus enters an inactive statefrom an active state, store a PDCP entity and an RLC entity of eachlogical channel, and reset a MAC entity and/or a physical channelconfiguration; or when the apparatus enters an inactive state from anactive state, store or configure a PDCP entity, and reset an RLC entityand/or a MAC entity and/or a physical channel configuration.

In a specific implementation, the identification information of theterminal includes: a unique identifier used to indicate the terminal inan access-network notification area in which the terminal is located; ora C-RNTI; or an identifier allocated by a core-network device.

In a specific implementation, the processing module 21 is furtherconfigured to obtain the configuration information preconfigured in aprotocol; or the apparatus further includes a receiving module 23,configured to receive the configuration information broadcast by theserving base station or sent by an anchor base station, where theconfiguration information includes at least one of feedback orretransmission configuration information, physical layer parameterconfiguration information, non-scheduled transmission configurationinformation, MAC layer control information, and channel configurationinformation.

The feedback or retransmission configuration information includes atleast one of the following: a HARQ process number, a retransmissionredundancy version, an indication about whether to reset MAC, a PDCCHtime-frequency resource used for feedback or downlink data sending, atiming relationship from uplink sending to downlink feedback, and atiming relationship from downlink sending to uplink feedback.

The physical layer parameter configuration information includes at leastone of the following: TTI duration, a CP length, a subcarrier spacing,and a physical channel type.

The non-scheduled transmission configuration information includes atleast one of the following: a quantity of times of non-scheduled uplinkblind retransmission, a non-scheduled automatic retransmission interval,non-scheduled transmission signal received power expected by a basestation, a non-scheduled transmission power boost step, a DRMS listavailable for non-scheduled transmission, and an MCS available fornon-scheduled transmission.

The MAC layer control information includes at least one of thefollowing: whether to report CSI, periodic or aperiodic CSI reporting, aCSI reporting class, whether to report a PHR, periodic or aperiodic PHRreporting, whether to report a BSR, a BSR reporting format, and periodicor aperiodic BSR reporting.

The channel configuration information includes at least one of thefollowing: an RLC configuration corresponding to a service channel, acorrespondence between a service channel and a flow identifier, and anRLC configuration corresponding to a control channel.

In a specific implementation, before the data is sent to the servingbase station based on the configuration information, the processingmodule 21 is further configured to: obtain the to-be-sent data; andperform encryption and/or integrity protection on the to-be-sent data byusing a pre-obtained key or a key currently obtained throughcalculation.

In a specific implementation, before the to-be-sent data is obtained,the receiving module 23 is further configured to receive indicationinformation sent by the anchor base station, where the indicationinformation is used to indicate whether the terminal needs to update akey; and if the indication information indicates that the terminal doesnot need to change the key, the processing module 21 determines that thekey obtained last time can still be used.

In a specific implementation, if the indication information indicatesthat the terminal needs to update the key, the processing module 21 isfurther configured to obtain a new key by performing deduction by usinga deduction parameter received last time; and the sending module 22 isfurther configured to send key update indication information to theserving base station, where the key update information may include thededuction parameter.

In a specific implementation, the processing module 21 is furtherconfigured to obtain new terminal identification information allocatedby the serving base station.

The data transmission apparatus provided in any one of the foregoingimplementations is configured to perform a technical solution on aterminal side in any one of the foregoing method embodiments. Animplementation principle and a technical effect thereof are similar.Details are not described herein again.

FIG. 9 is a schematic structural diagram of Embodiment 3 of a datatransmission apparatus according to an embodiment of this application.The data transmission apparatus 30 includes: a receiving module 31,configured to receive data sent by a serving base station, where thedata includes to-be-sent data sent by a terminal and identificationinformation of the terminal; a processing module 32, configured toobtain, based on the identification information of the terminal, linkinformation corresponding to the terminal; and a sending module 33,configured to send the data to a core-network device based on the linkinformation.

The data transmission apparatus provided in this embodiment isconfigured to perform a technical solution on an anchor base stationside in any one of the foregoing method embodiments. An implementationprinciple and a technical effect thereof are similar. Details are notdescribed herein again.

Based on the foregoing embodiment, the receiving module 31 is furtherconfigured to receive a logical channel identifier and/or a channel typethat are/is corresponding to the to-be-sent data and that are/is sent bythe serving base station, where the logical channel identifier isincluded in the data or not included in the data.

In a specific implementation, the receiving module 31 is furtherconfigured to receive new terminal identification information of theterminal sent by the serving base station.

In a specific implementation, the receiving module 31 is furtherconfigured to receive a terminal identity deletion instruction sent bythe serving base station; and the processing module 32 is furtherconfigured to delete the identification information of the terminalaccording to the terminal identity deletion instruction.

In a specific implementation, the sending module 33 is furtherconfigured to send, to the serving base station, configurationinformation and/or state information of an RLC entity corresponding tothe terminal.

The data transmission apparatus provided in any one of the foregoingimplementations is configured to perform a technical solution on ananchor base station side in any one of the foregoing method embodiments.An implementation principle and a technical effect thereof are similar.Details are not described herein again.

FIG. 10 is a schematic structural diagram of Embodiment 4 of a datatransmission apparatus according to an embodiment of this application.The data transmission apparatus 40 includes: a receiving module 41,configured to receive data sent by an anchor base station, where thedata includes to-be-sent data that is to be sent to a terminal andidentification information of the terminal; and a sending module 42,configured to send the to-be-sent data to the terminal.

In this solution, the identification information of the terminalincludes a unique identifier used to indicate the terminal in anaccess-network notification area in which the terminal is located, or aC-RNTI, or an identifier allocated by a core-network device.

The data transmission apparatus provided in this embodiment isconfigured to perform a technical solution on a serving base stationside in the data transmission method provided in any one of theforegoing method embodiments. An implementation principle and atechnical effect thereof are similar. Details are not described hereinagain.

FIG. 11 is a schematic structural diagram of Embodiment 5 of a datatransmission apparatus according to an embodiment of this application.The data transmission apparatus 50 includes: a receiving module 51,configured to receive data sent by a core-network device, where the dataincludes to-be-sent data that is to be sent to a terminal andidentification information of the terminal; a processing module 52,configured to determine a serving base station of the terminal based onthe identification information of the terminal; and a sending module 53,configured to send the data to the serving base station.

In this solution, the identification information of the terminalincludes a unique identifier used to indicate the terminal in anaccess-network notification area in which the terminal is located, or aC-RNTI, or an identifier allocated by a core-network device.

The data transmission apparatus provided in this embodiment isconfigured to perform a technical solution on an anchor base stationside in the data transmission method provided in any one of theforegoing method embodiments. An implementation principle and atechnical effect thereof are similar. Details are not described hereinagain.

An embodiment of this application further provides a base station. Thebase station provides an air interface for a terminal, and the basestation may interact with another base station. The base station is theserving base station in the foregoing solutions. The base stationincludes at least one processor, a memory, and a communicationsinterface (for example, a receiver and a transmitter). The at least oneprocessor, the memory, and the communications interface are connected toeach other by using a bus. The memory stores a computer executableinstruction. The at least one processor executes the computer executableinstruction stored in the memory, so that the base station exchangesdata with the another base station and a terminal through thecommunications interface, to perform a technical solution on a servingbase station side in the data transmission method provided in any one ofthe foregoing embodiments. An implementation principle and a technicaleffect thereof are similar.

An embodiment of this application further provides a terminal. Theterminal includes at least one processor, a memory, and a communicationsinterface (for example, the terminal transmits data by using a receiverand a transmitter). The at least one processor, the memory, and thecommunications interface are connected to each other by using a bus. Thememory stores a computer executable instruction. The at least oneprocessor executes the computer executable instruction stored in thememory, so that the terminal exchanges data with a serving base stationor an anchor base station through the communications interface, toperform a solution on a terminal side in the data transmission methodprovided in any one of the foregoing embodiments. An implementationprinciple and a technical effect thereof are similar.

An embodiment of this application further provides a base station. Thebase station may interact with another base station, and includes atleast one processor, a memory, and a communications interface (forexample, the base station transmits data by using a receiver and atransmitter). The at least one processor, the memory, and thecommunications interface are connected to each other by using a bus. Thememory stores a computer executable instruction. The at least oneprocessor executes the computer executable instruction stored in thememory, so that the base station exchanges data with the another basestation or a terminal through the communications interface, to perform atechnical solution on an anchor base station side in the datatransmission method provided in any one of the foregoing embodiments. Animplementation principle and a technical effect thereof are similar.

An embodiment of this application further provides a computer readablestorage medium. The computer readable storage medium stores a computerexecutable instruction. When at least one processor of a base stationexecutes the computer executable instruction, the base station performsa technical solution on a serving base station side in the datatransmission method provided in the foregoing various implementations.

An embodiment of this application further provides a computer readablestorage medium. The computer readable storage medium stores a computerexecutable instruction. When at least one processor of a terminalexecutes the computer executable instruction, the terminal performs thedata transmission method provided in any one of the foregoingembodiments.

An embodiment of this application further provides a computer readablestorage medium. The computer readable storage medium stores a computerexecutable instruction. When at least one processor of a base stationexecutes the computer executable instruction, the base station performsa technical solution for an anchor base station in the data transmissionmethod provided in any one of the foregoing embodiments.

An embodiment of this application further provides a computer programproduct. The computer program product includes a computer executableinstruction. The computer executable instruction is stored in a computerreadable storage medium. At least one processor of a base station mayread the computer executable instruction from the computer readablestorage medium, and the at least one processor executes the computerexecutable instruction, so that the base station implements a technicalsolution on a serving base station side in the data transmission methodprovided in the foregoing embodiments.

An embodiment of this application further provides a computer programproduct. The computer program product includes a computer executableinstruction. The computer executable instruction is stored in a computerreadable storage medium. At least one processor of a terminal may readthe computer executable instruction from the computer readable storagemedium, and the at least one processor executes the computer executableinstruction, so that the terminal implements the data transmissionmethod provided in the foregoing various implementations.

An embodiment of this application further provides a computer programproduct. The computer program product includes a computer executableinstruction. The computer executable instruction is stored in a computerreadable storage medium. At least one processor of a base station mayread the computer executable instruction from the computer readablestorage medium, and the at least one processor executes the computerexecutable instruction, so that the base station implements a technicalsolution on an anchor base station side in the data transmission methodprovided in the foregoing various implementations.

It should be understood that in the foregoing terminal or base stationembodiments, the processor may be a central processing unit (CPU), ormay be another general purpose processor, a digital signal processor(DSP), an application-specific integrated circuit (ASIC), or the like.The general purpose processor may be a microprocessor, or the processormay be any conventional processor or the like. The steps of the methodsdisclosed with reference to the embodiments of this application may bedirectly performed by a hardware processor, or may be performed by usinga combination of hardware in a processor and a software module.

All or some of the steps in the foregoing method embodiments may beimplemented by a program by instructing relevant hardware. The programmay be stored in a computer readable memory. When the program isexecuted, the steps in the foregoing method embodiments are performed.The memory (storage medium) includes: a read-only memory (ROM), a RAM, aflash memory, a hard disk, a solid state disk, a magnetic tape, a floppydisk, an optical disc, and any combination thereof.

Finally, it should be noted that the foregoing embodiments are merelyintended to describe the technical solutions of this application, butnot to limit this application.

What is claimed is:
 1. A device, wherein the device is a serving basestation or the device is an apparatus included in the serving basestation, the device comprising: at least one processor; and one or morememories storing programming instructions executable by the at least oneprocessor to perform operations comprising: receiving, from a terminal,identification information of the terminal in an inactive state, whereinthe identification information is allocated by an anchor base station ofthe terminal; determining the anchor base station of the terminalaccording to the identification information; and sending a cell radionetwork temporary identifier (C-RNTI) to the anchor base station,wherein the C-RNTI is allocated by the serving base station to theterminal.
 2. The device according to claim 1, wherein the operationsfurther comprise: receiving a logical channel identifier correspondingto to-be-sent data of the terminal; and sending, to the anchor basestation, an IP flow identifier, the logical channel identifier, or achannel type corresponding to the to-be-sent data.
 3. The deviceaccording to claim 1, wherein the identification information comprises:a unique identifier indicating the terminal in an access-networknotification area in which the terminal is located.
 4. The deviceaccording to claim 1, wherein the operations further comprise: beforereceiving the identification information, broadcasting configurationinformation, wherein the configuration information comprises: feedbackconfiguration information, retransmission configuration information,physical layer parameter configuration information, non-scheduledtransmission configuration information, media access control (MAC) layercontrol information, or channel configuration information; wherein thefeedback configuration information or the retransmission configurationinformation comprises: a hybrid automatic repeat request (HARQ) processnumber, a retransmission redundancy version, an indication about whetherto reset media access control (MAC), a physical downlink control channel(PDCCH) time-frequency resource used for feedback or downlink datasending, a timing relationship from uplink sending to downlink feedback,or a timing relationship from downlink sending to uplink feedback;wherein the physical layer parameter configuration informationcomprises: transmission time interval (TTI) duration, a cyclic prefix(CP) length, a subcarrier spacing, or a physical channel type; whereinthe non-scheduled transmission configuration information comprises: aquantity of times of non-scheduled uplink blind retransmission, anon-scheduled automatic retransmission interval, non-scheduledtransmission signal received power expected by a base station, anon-scheduled transmission power boost step, a demodulation referencesignal (DRMS) list available for non-scheduled transmission, or amodulation and coding scheme (MCS) available for non-scheduledtransmission; wherein the MAC layer control information comprises:whether to report channel state information (CSI), periodic or aperiodicCSI reporting, a CSI reporting class, whether to report a power headroomreport (PHR), periodic or aperiodic PHR reporting, whether to report abuffer status report (BSR), a BSR reporting format, or periodic oraperiodic BSR reporting; and wherein the channel configurationinformation comprises: a radio link control (RLC) configurationcorresponding to a service channel, a correspondence between a servicechannel and a flow identifier, or an RLC configuration corresponding toa control channel.
 5. The device according to claim 1, wherein theoperations further comprise: receiving key update indication informationfrom the terminal.
 6. The device according to claim 1, wherein theoperations further comprise: establishing a media access control (MAC)entity or a radio link control (RLC) entity corresponding to theterminal; or receiving configuration information or state information,from the anchor base station, of an RLC entity corresponding to theterminal.
 7. The device according to claim 1, wherein: the C-RNTI isallocated by the serving base station to the terminal during randomaccess channel (RACH) data transmission; or the C-RNTI is allocated bythe serving base station to the terminal during radio access networknotification area location update notification.
 8. The device accordingto claim 1, wherein the operations further comprise: sending anidentifier of a cell that allocates the C-RNTI to the anchor basestation, wherein the cell is of the serving base station.
 9. The deviceaccording to claim 1, wherein the operations further comprises:receiving data from the terminal; and sending the data to the anchorbase station.
 10. A device, wherein the device is an anchor base stationof a terminal, or the device is an apparatus included in the anchor basestation of the terminal, the device comprising: at least one processor;and one or more memories storing programming instructions executable bythe at least one processor to perform operations comprising: allocating,to the terminal, identification information of the terminal for theterminal to use in an inactive state; receiving a cell radio networktemporary identifier (C-RNTI) from a serving base station of theterminal, wherein the C-RNTI is allocated by the serving base station ofthe terminal to the terminal; and updating a context of the terminal inthe anchor base station according to the C-RNTI.
 11. The deviceaccording to claim 10, wherein the operations further comprise:receiving an IP flow identifier, a logical channel identifier, or achannel type corresponding to to-be-sent data of the terminal that issent by the serving base station.
 12. The device according to claim 10,wherein the operations further comprise: receiving a terminal identitydeletion instruction from the serving base station; and deleting theidentification information of the terminal according to the terminalidentity deletion instruction.
 13. The device according to claim 10,wherein the operations further comprise: sending configurationinformation to the terminal, wherein the configuration informationcomprises: feedback configuration information, retransmissionconfiguration information, physical layer parameter configurationinformation, non-scheduled transmission configuration information, mediaaccess control (MAC) layer control information, or channel configurationinformation; wherein the feedback configuration information or theretransmission configuration information comprises: a hybrid automaticrepeat request (HARQ) process number, a retransmission redundancyversion, an indication about whether to reset media access control(MAC), a physical downlink control channel (PDCCH) time-frequencyresource used for feedback or downlink data sending, a timingrelationship from uplink sending to downlink feedback, or a timingrelationship from downlink sending to uplink feedback; wherein thephysical layer parameter configuration information comprises:transmission time interval (TTI) duration, a cyclic prefix (CP) length,a subcarrier spacing, or a physical channel type; wherein thenon-scheduled transmission configuration information comprises: aquantity of times of non-scheduled uplink blind retransmission, anon-scheduled automatic retransmission interval, non-scheduledtransmission signal received power expected by a base station, anon-scheduled transmission power boost step, a demodulation referencesignal (DRMS) list available for non-scheduled transmission, or amodulation and coding scheme (MCS) available for non-scheduledtransmission; wherein the MAC layer control information comprises:whether to report channel state information (CSI), periodic or aperiodicCSI reporting, a CSI reporting class, whether to report a power headroomreport (PHR), periodic or aperiodic PHR reporting, whether to report abuffer status report (BSR), a BSR reporting format, or periodic oraperiodic BSR reporting; and wherein the channel configurationinformation comprises: a radio link control (RLC) configurationcorresponding to a service channel, a correspondence between a servicechannel and a flow identifier, or an RLC configuration corresponding toa control channel.
 14. The device according to claim 10, wherein theoperations further comprise: receiving, from the serving base station,an identifier of a cell that allocates the C-RNTI, wherein the cell isof the serving base station.
 15. The device according to claim 10,wherein the operations further comprise: receiving data of the terminalfrom the serving base station.
 16. A communication system, comprising: aserving base station; and an anchor base station; wherein the servingbase station is configured to: receive, from a terminal in an inactivestate, identification information of the terminal in the inactive state;determine the anchor base station according to the identificationinformation; and send a cell radio network temporary identifier (C-RNTI)to the anchor base station, wherein the C-RNTI is allocated by theserving base station to the terminal; and wherein the anchor basestation is configured to: allocate the identification information to theterminal; receive the C-RNTI from the serving base station; and update acontext of the terminal in the anchor base station according to theC-RNTI.
 17. The system according to claim 16, wherein the identificationinformation comprises: a unique identifier indicating the terminal in anaccess-network notification area in which the terminal is located. 18.The system according to claim 16, wherein: the C-RNTI is allocated bythe serving base station to the terminal during random access channel(RACH) data transmission; or the C-RNTI is allocated by the serving basestation to the terminal during radio access network notification arealocation update notification.
 19. The system according to claim 16,wherein the serving base station is further configured to: send anidentifier of a cell that allocates the C-RNTI to the anchor basestation, wherein the cell is of the serving base station; and whereinthe anchor base station is further configured to: receive the identifierof the cell from the serving base station.
 20. The system according toclaim 16, wherein the serving base station is further configured to:receive data from the terminal; and send the data to the anchor basestation.